426 Satellite Newsgathering Azimuth Angle of rotation (horizontal) that a parabolic antenna must be rotated through to point to a specific satellite in a geosynchronous orbit; the compass bearing of the satellite in the horizontal plane from a point on the Earth's surface. Backhaul Contribution circuit: traditionally a terrestrial communications path linking an earth station to a local switching network; now also refers to satellite contribution paths. Back-off Process of reducing the input and output power levels of a traveling wave tube to obtain more linear operation and hence minimize the risk of distortion. Expressed in dB. Bandpass filter Active or passive circuit which allows signals within the desired frequency band to pass but prevents signals outside this pass band from getting through. Bandwidth Measure of spectrum (frequency) use or capacity; the amount of information that can be passed at a given time over a certain span of frequency. BAP Binary Alpha Plane (MPEG-4). Baseband Basic direct output signal obtained directly from a camera or videotape recorder or other video source. Basic rate ISDN ISDN service of 2 64 kbps bearers and a 16 kbps data control channel. Also referred to as 2B D. Baud Rate of data transmission based on the number of symbols transmitted per second; see Symbol. BBC British Broadcasting Corporation: UK network formed in 1927 from the British Broadcasting Company established in 1922. Beacon Low-power carrier transmitted by a satellite which provides the satellite operations control